A 3rd generation partnership project long term evolution (3GPP LTE) or LTE-Advanced (LTE-A) communication system which is an example of a mobile communication system to which the present invention may be applied will be described in brief.
One or more cells may exist for one base station. One cell is set to one of bandwidths of 1.25, 2.5, 5, 10, and 20 MHz to provide a downlink or uplink transport service to several user equipment. Different cells may be set to provide different bandwidths. Also, one base station controls data transmission and reception for a plurality of user equipment. The base station transmits downlink (DL) scheduling information of downlink data to the corresponding user equipment to notify the user equipment of time and frequency domains to which data will be transmitted and information related to encoding, data size, hybrid automatic repeat and request (HARQ). Also, the base station transmits uplink (UL) scheduling information of uplink data to the corresponding user equipment to notify the user equipment of time and frequency domains that can be used by the corresponding user equipment, and information related to encoding, data size, and HARQ. An interface for transmitting user traffic or control traffic may be used between the base stations.
Although the wireless communication technology developed based on WCDMA has been evolved into LTE, request and expectation of users and providers have continued to increase. Also, since another wireless access technology is being continuously developed, new evolution of the wireless communication technology will be required for competitiveness in the future. In this respect, reduction of cost per bit, increase of available service, use of adaptable frequency band, simple structure, open type interface, proper power consumption of the user equipment, etc. are required.
Recently, standardization of advanced technology of LTE is in progress under the 3rd Generation Partnership Project (3GPP). This technology will be referred to as “LTE-Advanced” or “LTE-A.” One of important differences between the LTE system and the LTE-A system is difference in system bandwidth and introduction of a relay station.
However, a method for contention based uplink data transmission of an LTE-A user equipment which is not scheduled for uplink resources from a base station in the LTE-A system has not been studied until now.